OC 自带方法简绍 5 NSDictionary

最新推荐文章于 2021-05-19 14:50:41 发布

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最新推荐文章于 2021-05-19 14:50:41 发布

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本文链接：https://blog.youkuaiyun.com/qq_25173057/article/details/42842757

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这篇博客介绍了 Objective-C 中的 NSDictionary 类的一些基本操作，包括使用 initWithObjectsAndKeys 初始化字典，通过 objectForKey 获取值，使用 setObject 添加数据，removeObjectForKey 删除数据，以及如何遍历字典。还提到了其可变子类 NSMutableDictionary 和相关操作如 removeAllObjects 清空字典。

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1.字典

initWithObjectsAndKeys ; 初始化字典

dictionaryWithObjectsAndKeys : 初始化字典

dictionaryWithObjects forKeys:

1.1

NSDictionary * dic = [[NSDictionary alloc] initWithObjectsAndKeys:@"m", @"sex", @"25", @"age", @"zhangsan", @"name",nil];
NSLog(@"%@", dic);

1.2

NSDictionary * dic2 = [NSDictionary dictionaryWithObjectsAndKeys:@"zhangsan", @"name", @"21", @"age",nil];
NSLog(@"%@", dic2);

1.3

NSArray * valueArray = [NSArray arrayWithObjects:@"fulushou", @"M", @"25", nil];
NSArray * keyArray = [NSArray arrayWithObjects:@"name", @"sex", @"age", nil];

NSDictionary * dic = [NSDictionary dictionaryWithObjects:valueArray forKeys:keyArray];
NSLog(@"%@", dic);

2.//count // allKeys //allValues // 对数 , 所有的键 , 所有的值

@property(readonly) NSUInteger count //The number of entries in the dictionary (read-only)

@property(readonly, copy) NSArray *allKeys //A new array containing the dictionary’s keys, or an empty array if the dictionary has no entries (read-only)

例子

        NSLog(@"%lu", [dic count]);
        NSLog(@"%@", [dic allKeys]);
        NSLog(@"%@", [dic allValues]);

3.objectForKey 通过键获取值字典中的值

- (id)objectForKey:(NSString *)key // Returns the value for the given key stored in the record.

例子

NSString * str = [dic objectForKey:@"name"];
NSLog(@"%@", str);

        // 怎么遍历字典 ? 方法一
        for (int i = 0; i < [dic count]; i++) {
            NSString * value = [[dic allKeys] objectAtIndex:i];
            NSLog(@"%@", [dic objectForKey:value]);
        }

        for (int i = 0; i < [dic count]; i++) {
            NSString * value = [[dic allValues] objectAtIndex:i];
            NSLog(@"%@", value);
        }

4.NSMutableDictionary //继承自Dictdonary 的可改变的字典

NSMutableDictionary * dic = [NSMutableDictionary dictionaryWithCapacity:1];

5.setObject //给字典添加数据

virtual bool setObject( const char *aKey, const OSMetaClassBase *anObject); //Stores an object in the dictionary under a key.

例子

//        [dic setObject:@"fulushou" forKey:@"name"];
//        [dic setObject:@"M" forKey:@"sex"];
//        [dic setObject:@"25" forKey:@"age"];

6.removeObjectForKey //通过key 删除字典中数据

- (void)removeObjectForKey:(NSString *)defaultName //Removes the value of the specified default key in the standard application domain.

例子

[dic removeObjectForKey:@"age2"];
NSLog(@"%@", dic);

7.arrayWithObjects //批量删除字典中数据

+ (instancetype)arrayWithObjects:(id)firstObj , ... //Creates and returns an array containing the objects in the argument list.

        NSArray * arr = [NSArray arrayWithObjects:@"age", @"sex", nil];
        [dic removeObjectsForKeys:arr];
        NSLog(@"%@", dic);